Coasts

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Geography notes

Coasts

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Coasts are the boundary where the land meets the sea. The littoral zone includes land and the offshore parts of the sea which are shallow. Wave processes meet the foreshore. The near shore has lots of human activity like tourism and transport. The littoral zone extends from the backshore zone that is rarely covered in water to the offshore zone that is submerged.

The offshore zone is permanently submerged and sediment is only affected by storms.

Rocky coasts have hard rock and varying cliff heights. Hangman’s cliff in Devon is very tall at over 300m. Cornwall has resistant rock on the south west such as granite, slate and sandstone. These coastlines are high energy with more erosion that deposition so headlands, cliffs and shore-line platforms form in Atlantic facing beaches like Cornwall.

Coastal plains are gradually sloping sand dunes. They are weaker, younger sedimentary rock such as chalk and clay. The Wash is the largest UK estuary. It is very low, flat relief, mudflats, lagoons and low lying sandy beaches like Bamburgh beach. They are largely along the East and South UK coast. Sandy beaches are low energy with sheltered, less powerful waves. There is more deposition that erosion so beaches, spits and poorly drained plains occur.

Rock resistance depends on the reactiveness of minerals, whether they are clastic or crystalline and whether cracks are exposed.

Cliffs have an abrupt transition and vertical ones often expose the foreshore like a platform. Sandy dunes are inundated at high tide. Estuaries are exposed at low tide.

Coasts can be classified in many different ways. Primary coasts are formed by land driven process like place tectonics, land erosion and sedimentation. They have deposition coasts like the Nile Delta. Secondary coasts are formed my marine processes like wave erosion or the growth of coral reefs. These form when ocean sediments accumulate in a single place like barrier islands. Emergent coasts rise relative to sea level and submergent coasts are flooded by the sea. Microtidal coasts have a tidal range variation of 0-2m, mesotidal coasts have a tidal range variation of 2-4m and macrotidal coasts have a tidal range variation of 4+m. Low energy coasts have small fetches and weak winds.

Cliff profiles show the height, angle and features of a cliff face. Gentle cliff faces have sub-aerial processes moving rock down but it remains at the base and isn’t moved away as there is little erosion. Cliffs are shaped by inputs like waves or human change which cause processes like weathering or erosion and cause outputs like certain landforms. Littoral zones are changing due to waves, tides, sea level changes and climate change.

Weathering and erosion produces sediment which is transported and deposited as landforms. Mass movement, weathering and surface run off affect less resistant rocks more than resistant rocks. Unconsolidated rock is the weakest like gravel.

Lithology looks at strata which is the layers of rock, bedding planes which are natural breaks in the strata, joints, folds, faults which…

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